Method for determining SSC mode and apparatus

Abstract

A method for determining a service and session continuity (SSC) mode and an apparatus, where the method includes: determining, by a terminal device, a requested SSC mode; and sending a first request message to a first core network element, where the first request message is used to request to establish a first protocol data unit (PDU) session, and the first request message includes a session type of the first PDU session, the requested SSC mode, and first indication information. The first request message sent by the terminal device to the first core network element may carry the first indication information, used to indicate that the SSC mode requested by the terminal device is not allowed to be modified, to prevent a network-side network element from subsequently making an erroneous decision, for example, modifying the requested SSC mode to another SSC mode that is not supported by the terminal device.

What is claimed is: 
     
       1. A method, comprising:
 determining a requested service and session continuity (SSC) mode; 
 sending a first request message to a first core network element, wherein the first request message is a request for establishing a first protocol data unit (PDU) session with a first session type by using the requested SSC mode, and wherein the first session type is any one of an Internet Protocol (IP) session type, an Ethernet session type, or an unstructured session type; 
 receiving, in response to sending the first request message, a first response message from the first core network element, wherein the first response message indicates that the request for establishing the first PDU session is rejected, wherein the first response message comprises a cause code and an allowed SSC mode that is allowed for the first session type, wherein the allowed SSC mode is different than the requested SSC mode, and wherein the cause code indicates that the requested SSC mode is not supported; and 
 reattempting, in response to the cause code, to establish the first PDU session with the first session type by using the allowed SSC mode that is allowed for the first session type. 
 
     
     
       2. The method of  claim 1 , wherein the first request message further comprises first indication information, and wherein the first indication information indicates that the requested SSC mode is not allowed to be modified. 
     
     
       3. The method of  claim 1 , further comprising receiving first SSC mode limitation information, wherein the first SSC mode limitation information comprises at least one available session type and at least one associated available SSC mode, and wherein determining the requested SSC mode comprises determining, based on the first SSC mode limitation information, the requested SSC mode. 
     
     
       4. The method of  claim 3 , wherein the first SSC mode limitation information is associated with subscription information, and wherein the subscription information indicates at least one allowed session type and at least one associated allowed SSC mode. 
     
     
       5. The method of  claim 3 , wherein the requested SSC mode is a unique SSC mode that meets the first SSC mode limitation information. 
     
     
       6. The method of  claim 1 , wherein determining the requested SSC mode comprises obtaining the requested SSC mode according to a default SSC mode selection policy rule. 
     
     
       7. An apparatus, comprising:
 a memory configured to store instructions; and 
 one or more processors coupled to the memory and configured to execute the instructions to cause the apparatus to:
 determine a requested service and session continuity (SSC) mode; 
 send a first request message to a first core network element, wherein the first request message is a request for establishing a first protocol data unit (PDU) session with a first session type by using the requested SSC mode, and wherein the first session type is any one of an Internet Protocol (IP) session type, an Ethernet session type, or an unstructured session type; 
 receive, in response to sending the first request message, a first response message from the first core network element, wherein the first response message indicates that the request for establishing the first PDU session is rejected, wherein the first response message comprises a cause code and an allowed SSC mode that is allowed for the first session type, wherein the allowed SSC mode is different than the requested SSC mode, and wherein the cause code indicates that the requested SSC mode is not supported; and 
 reattempt, in response to the cause code, to establish the first PDU session with the first session type by using the allowed SSC mode that is allowed for the first session type. 
 
 
     
     
       8. The apparatus of  claim 7 , wherein the one or more processors are further configured to execute the instructions to cause the apparatus to:
 receive first SSC mode limitation information, wherein the first SSC mode limitation information comprises at least one available session type and at least one associated available SSC mode for the apparatus; and 
 determine the requested SSC mode based on the first SSC mode limitation information. 
 
     
     
       9. The apparatus of  claim 8 , wherein the first SSC mode limitation information is associated with subscription information of the apparatus, and wherein the subscription information indicates at least one allowed session type and at least one associated allowed SSC mode for the apparatus. 
     
     
       10. The apparatus of  claim 7 , wherein the one or more processors are further configured to execute the instructions to cause the apparatus to obtain the requested SSC mode according to a default SSC mode selection policy rule. 
     
     
       11. The apparatus of  claim 7 , wherein the apparatus comprises a terminal device or a chip in the terminal device. 
     
     
       12. A computer program product comprising instructions stored on a non-transitory computer-readable medium that, when executed by one or more processors of an apparatus, cause the apparatus to:
 determine a requested service and session continuity (SSC) mode; 
 send a first request message to a first core network element, wherein the first request message is a request for establishing a first protocol data unit (PDU) session with a first session type by using the requested SSC mode, and wherein the first session type is any one of an Internet Protocol (IP) session type, an Ethernet session type, or an unstructured session type; 
 receive, in response to sending the first request message, a first response message from the first core network element, wherein the first response message indicates that the request for establishing the first PDU session is rejected, wherein the first response message comprises a cause code and an allowed SSC mode that is allowed for the first session type, wherein the allowed SSC mode is different than the requested SSC mode, and wherein the cause code indicates that the requested SSC mode is not supported; and 
 reattempt, in response to the cause code, to establish the first PDU session with the first session type by using the allowed SSC mode that is allowed for the first session type. 
 
     
     
       13. The computer program product of  claim 12 , wherein the first request message further comprises first indication information, and wherein the first indication information indicates that the requested SSC mode is not allowed to be modified. 
     
     
       14. The computer program product of  claim 12 , wherein the one or more processors are further configured to execute the instructions to cause the apparatus to:
 receive first SSC mode limitation information, wherein the first SSC mode limitation information comprises at least one available session type and at least one associated available SSC mode for the apparatus; and 
 determine the requested SSC mode based on the first SSC mode limitation information. 
 
     
     
       15. The computer program product of  claim 14 , wherein the first SSC mode limitation information is associated with subscription information of the apparatus, and wherein the subscription information indicates at least one allowed session type and at least one associated allowed SSC mode for the apparatus. 
     
     
       16. The computer program product of  claim 12 , wherein the one or more processors are further configured to execute the instructions to cause the apparatus to obtain the requested SSC mode according to a default SSC mode selection policy rule. 
     
     
       17. The method of  claim 1 , wherein the first session type is the unstructured session type or the Ethernet session type, and wherein the requested SSC mode is SSC mode 3. 
     
     
       18. The apparatus of  claim 7 , wherein the first session type is the unstructured session type or the Ethernet session type, and wherein the requested SSC mode is SSC mode 3. 
     
     
       19. The computer program product of  claim 12 , wherein the first session type is the unstructured session type or the Ethernet session type, and wherein the requested SSC mode is SSC mode 3.